1. Field of the Invention
The present invention relates generally to a power supply installation for a direct current (dc) electric railroad and more specifically to a power supply installation by which an alternating current (ac) power is converted into a dc current power before being supplied to electric cars as a powering source.
2. Description of the Prior Art
Usually, a plurality of dc substations are installed at appropriate intervals along a railroad track. In these dc substations, a plurality of converters are arranged. The dc power output side of the converter is connected to each electric car power supply lines through each semiconductor breaker and the ac power input side thereof is directly connected in common with a power conductor. In other words, plural power supply circuits having power rectifiers and high-speed dc breakers are connected in parallel with each other between substations so as to construct a dc power supply installation.
On the other hand, the electric car power supply lines are divided into plural sections, and each of the above divided electric car power supply lines is connected to a positive bus bar through a high-speed breaker provided for each electric car power supply line and the electric car rails are connected to a negative bus bar at each substation.
In the prior art power supply installation for a dc railroad, however, there exist various drawbacks as follows: (1) In case the power rectifier fails in commutation, the influence of an accident due to the commutation failure tends to spread. (2) Once the regenerative breaker is turned off, the power is suspended for all the adjacent power supply lines. (3) The interruption capacity of the regenerative breaker should be great because the regenerative current and plural extension power supply current should be interrupted. (4) To reduce the interruption capacity of the regenerative breaker, it is necessary to interrupt the extension powering current at the adjacent substation. This operation complicates the operation sequence against accident and therefore lowers the reliability of the installation. (5) In the case of a double track, since four powering breakers should be provided, the installation is costly.
The arrangement of the prior art power supply installation for a direct current railroad will be described in further detail hereinafter with reference to FIG. 1 under Detailed Description of the Preferred Embodiments.